U.S. patent number 9,280,016 [Application Number 14/171,092] was granted by the patent office on 2016-03-08 for liquid crystal display device.
This patent grant is currently assigned to Japan Display Inc.. The grantee listed for this patent is Japan Display, Inc.. Invention is credited to Hirokazu Morimoto, Keiji Tago.
United States Patent |
9,280,016 |
Tago , et al. |
March 8, 2016 |
Liquid crystal display device
Abstract
According to one embodiment, a liquid crystal display device
includes a first substrate including a transmissive pixel electrode
disposed in a transmissive display area, and a reflective pixel
electrode with a planar plate shape which is disposed in a
reflective display area, a second substrate including a common
electrode, a liquid crystal layer being configured to have a less
thickness in the reflective display area than in the transmissive
display area, to impart a phase difference of 1/4 wavelength to
light passing at an OFF time in the reflective display area, and to
impart no phase difference to light passing at an ON time in the
reflective display area, and a retardation plate disposed between a
second polarizer and the second substrate in the reflective display
area.
Inventors: |
Tago; Keiji (Tokyo,
JP), Morimoto; Hirokazu (Tokyo, JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
Japan Display, Inc. |
Minato-ku |
N/A |
JP |
|
|
Assignee: |
Japan Display Inc. (Minato-ku,
JP)
|
Family
ID: |
51350923 |
Appl.
No.: |
14/171,092 |
Filed: |
February 3, 2014 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20140232953 A1 |
Aug 21, 2014 |
|
Foreign Application Priority Data
|
|
|
|
|
Feb 18, 2013 [JP] |
|
|
2013-028837 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G02F
1/133555 (20130101); G02F 1/133371 (20130101); G02F
1/13439 (20130101); G02F 1/133638 (20210101) |
Current International
Class: |
G02F
1/1335 (20060101); G02F 1/1343 (20060101); G02F
1/1333 (20060101); G02F 1/13363 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
6-222397 |
|
Aug 1994 |
|
JP |
|
7-159807 |
|
Jun 1995 |
|
JP |
|
9-160041 |
|
Jun 1997 |
|
JP |
|
9-160042 |
|
Jun 1997 |
|
JP |
|
9-160061 |
|
Jun 1997 |
|
JP |
|
10-26765 |
|
Jan 1998 |
|
JP |
|
10-90708 |
|
Apr 1998 |
|
JP |
|
2005-3802 |
|
Jan 2005 |
|
JP |
|
3644653 |
|
May 2005 |
|
JP |
|
2005-242307 |
|
Sep 2005 |
|
JP |
|
2012-113332 |
|
Jun 2012 |
|
JP |
|
Primary Examiner: Nguyen; Dung
Attorney, Agent or Firm: Oblon, McClelland, Maier &
Neustadt, L.L.P.
Claims
What is claimed is:
1. A liquid crystal display device comprising: a first substrate
including a transmissive pixel electrode which is disposed in a
transmissive display area and includes a main pixel electrode with
a strip shape extending in a second direction, a reflective pixel
electrode with a planar plate shape which is disposed in a
reflective display area, and a shield electrode which is disposed
in the transmissive display area; a second substrate including a
common electrode which includes a plate electrode with a planar
plate shape opposed to the reflective pixel electrode, the common
electrode having the same potential as the shield electrode; a
liquid crystal layer including liquid crystal molecules held
between the first substrate and the second substrate, the liquid
crystal layer being configured to have a less thickness in the
reflective display area than in the transmissive display area, to
impart a phase difference of 1/4 wavelength to light passing at an
OFF time in the reflective display area, and to impart no phase
difference to light passing at an ON time in the reflective display
area; a first polarizer disposed on an outside of the first
substrate and having a first polarization axis; a second polarizer
disposed on an outside of the second substrate and having a second
polarization axis which is perpendicular to the first polarization
axis; and a retardation plate disposed between the second polarizer
and the second substrate in the reflective display area, and
configured to impart a phase difference of 1/2 wavelength.
2. The liquid crystal display device of claim 1, wherein the common
electrode further includes main common electrodes extending in the
second direction on both sides of the main pixel electrode.
3. The liquid crystal display device of claim 2, wherein the first
substrate includes a first alignment film covering the transmissive
pixel electrode, the reflective pixel electrode and the shield
electrode, the second substrate includes a second alignment film
covering the common electrode, and a first alignment treatment
direction of the first alignment film and a second alignment
treatment direction of the second alignment film are parallel and
opposite to each other.
4. The liquid crystal display device of claim 3, wherein the first
alignment treatment direction is parallel to the second
direction.
5. The liquid crystal display device of claim 4, wherein the liquid
crystal molecules are homogeneously aligned in a state in which no
electric field is produced between the transmissive pixel electrode
and the reflective pixel electrode, on one hand, and the common
electrode, on the other hand.
6. The liquid crystal display device of claim 1, further comprising
a protection plate disposed to be opposed to the second polarizer,
wherein the protection plate includes light-shield portions which
are disposed, respectively, on an outside of the transmissive
display area and the reflective display area, and at a boundary
between the transmissive display area and the reflective display
area.
7. The liquid crystal display device of claim 6, wherein the
protection plate includes a touch sensor.
8. The liquid crystal display device of claim 1, wherein the
transmissive pixel electrode and the reflective pixel electrode are
formed of the same electrically conductive material.
9. The liquid crystal display device of claim 8, wherein the
electrically conductive material is opaque.
10. A liquid crystal display device comprising: a first substrate
including a transmissive pixel electrode disposed in a transmissive
display area, and a reflective pixel electrode disposed in a
reflective display area; a second substrate including a common
electrode which is formed to extend over the transmissive display
area and the reflective display area; a liquid crystal layer
including liquid crystal molecules held between the first substrate
and the second substrate, the liquid crystal layer being configured
to have a less thickness in the reflective display area than in the
transmissive display area, to impart a phase difference of 1/4
wavelength to light passing at an OFF time in the reflective
display area, and to impart no phase difference to light passing at
an ON time in the reflective display area; a first polarizer
disposed on an outside of the first substrate and having a first
polarization axis; a second polarizer disposed on an outside of the
second substrate and having a second polarization axis which is
perpendicular to the first polarization axis; and a retardation
plate disposed between the second polarizer and the second
substrate in the reflective display area, and configured to impart
a phase difference of 1/2 wavelength.
11. The liquid crystal display device of claim 10, wherein the
transmissive pixel electrode includes a main pixel electrode with a
strip shape extending in a second direction, and the common
electrode includes main common electrodes extending in the second
direction on both sides of the main pixel electrode.
12. The liquid crystal display device of claim 10, wherein the
reflective pixel electrode is formed in a planar plate shape, and
the common electrode includes a plate electrode with a planar plate
shape opposed to the reflective pixel electrode.
13. The liquid crystal display device of claim 10, wherein the
transmissive pixel electrode includes a main pixel electrode with a
strip shape extending in a second direction, and the first
substrate further includes shield electrodes which are disposed on
both sides of the transmissive pixel electrode.
14. The liquid crystal display device of claim 10, wherein the
first substrate includes a first alignment film covering the
transmissive pixel electrode and the reflective pixel electrode,
the second substrate includes a second alignment film covering the
common electrode, and a first alignment treatment direction of the
first alignment film and a second alignment treatment direction of
the second alignment film are parallel and opposite to each
other.
15. The liquid crystal display device of claim 14, wherein the
first alignment treatment direction is parallel to the second
direction.
16. The liquid crystal display device of claim 15, wherein the
liquid crystal molecules are homogeneously aligned in a state in
which no electric field is produced between the transmissive pixel
electrode and the reflective pixel electrode, on one hand, and the
common electrode, on the other hand.
17. The liquid crystal display device of claim 10, further
comprising a protection plate disposed to be opposed to the second
polarizer, wherein the protection plate includes light-shield
portions which are disposed, respectively, on an outside of the
transmissive display area and the reflective display area, and at a
boundary between the transmissive display area and the reflective
display area.
18. The liquid crystal display device of claim 17, wherein the
protection plate includes a touch sensor.
19. The liquid crystal display device of claim 10, wherein the
transmissive pixel electrode and the reflective pixel electrode are
formed of the same electrically conductive material.
20. The liquid crystal display device of claim 19, wherein the
electrically conductive material is opaque.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is based upon and claims the benefit of priority
from Japanese Patent Application No. 2013-028837, filed Feb. 18,
2013, the entire contents of which are incorporated herein by
reference.
FIELD
Embodiments described herein relate generally to a liquid crystal
display device.
BACKGROUND
In recent years, flat-panel display devices have been vigorously
developed. By virtue of such advantageous features as light weight,
small thickness and low power consumption, special attention has
been paid to liquid crystal display devices among others. In
particular, in active matrix liquid crystal display devices in
which switching elements are incorporated in respective pixels,
attention is paid to the configuration which makes use of a lateral
electric field (including a fringe electric field), such as an IPS
(In-Plane Switching) mode or an FFS (Fringe Field Switching) mode.
Such a liquid crystal display device of the lateral electric field
mode includes pixel electrodes and a counter-electrode, which are
formed on an array substrate, and liquid crystal molecules are
switched by a lateral electric field which is substantially
parallel to a major surface of the array substrate.
On the other hand, there has been proposed a technique of switching
liquid crystal molecules by producing a lateral electric field or
an oblique electric field between pixel electrodes formed on the
array substrate and a counter-electrode formed on the
counter-substrate.
The power consumption of the liquid crystal display device
increases as the screen size becomes larger. This is a factor of
limiting the time of use, for example, when the liquid crystal
display device is mounted on a portable electronic apparatus.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a view which schematically illustrates a structure and an
equivalent circuit of a liquid crystal display device according to
an embodiment.
FIG. 2 is a cross-sectional view, taken along line II-II in FIG. 1,
which schematically illustrates an example of a cross section of a
liquid crystal display panel shown in FIG. 1.
FIG. 3 is a plan view which schematically illustrates a structure
example of one pixel at a time when a transmissive display area of
the liquid crystal display panel shown in FIG. 1 is viewed from a
counter-substrate side.
FIG. 4 is a plan view which schematically illustrates a structure
example of one pixel at a time when a reflective display area of
the liquid crystal display panel shown in FIG. 1 is viewed from the
counter-substrate side.
FIG. 5 is a cross-sectional view of a liquid crystal display panel
LPN at a time when a transmissive display area A1 is cut along line
A-A in FIG. 3, and a cross-sectional view of the liquid crystal
display panel LPN at a time when a reflective display area A2 is
cut along line B-B in FIG. 4.
FIG. 6 is another cross-sectional view of the liquid crystal
display panel LPN at a time when the transmissive display area A1
is cut along line A-A in FIG. 3, and another cross-sectional view
of the liquid crystal display panel LPN at a time when the
reflective display area A2 is cut along line B-B in FIG. 4.
FIG. 7 is another cross-sectional view of the liquid crystal
display panel LPN at a time when the transmissive display area A1
is cut along line A-A in FIG. 3, and another cross-sectional view
of the liquid crystal display panel LPN at a time when the
reflective display area A2 is cut along line B-B in FIG. 4.
DETAILED DESCRIPTION
In general, according to one embodiment, a liquid crystal display
device includes: a first substrate including a transmissive pixel
electrode which is disposed in a transmissive display area and
includes a main pixel electrode with a strip shape extending in a
second direction, a reflective pixel electrode with a planar plate
shape which is disposed in a reflective display area, and a shield
electrode which is disposed in the transmissive display area; a
second substrate including a common electrode which includes a
plate electrode with a planar plate shape opposed to the reflective
pixel electrode, the common electrode having the same potential as
the shield electrode; a liquid crystal layer including liquid
crystal molecules held between the first substrate and the second
substrate, the liquid crystal layer being configured to have a less
thickness in the reflective display area than in the transmissive
display area, to impart a phase difference of 1/4 wavelength to
light passing at an OFF time in the reflective display area, and to
impart no phase difference to light passing at an ON time in the
reflective display area; a first polarizer disposed on an outside
of the first substrate and having a first polarization axis; a
second polarizer disposed on an outside of the second substrate and
having a second polarization axis which is perpendicular to the
first polarization axis; and a retardation plate disposed between
the second polarizer and the second substrate in the reflective
display area, and configured to impart a phase difference of 1/2
wavelength.
According to one embodiment, a liquid crystal display device
includes: a first substrate including a transmissive pixel
electrode disposed in a transmissive display area, and a reflective
pixel electrode disposed in a reflective display area; a second
substrate including a common electrode which is formed to extend
over the transmissive display area and the reflective display area;
a liquid crystal layer including liquid crystal molecules held
between the first substrate and the second substrate, the liquid
crystal layer being configured to have a less thickness in the
reflective display area than in the transmissive display area, to
impart a phase difference of 1/4 wavelength to light passing at an
OFF time in the reflective display area, and to impart no phase
difference to light passing at an ON time in the reflective display
area; a first polarizer disposed on an outside of the first
substrate and having a first polarization axis; a second polarizer
disposed on an outside of the second substrate and having a second
polarization axis which is perpendicular to the first polarization
axis; and a retardation plate disposed between the second polarizer
and the second substrate in the reflective display area, and
configured to impart a phase difference of 1/2 wavelength.
Embodiments will now be described in detail with reference to the
accompanying drawings. In the drawings, structural elements having
the same or similar functions are denoted by like reference
numerals, and an overlapping description is omitted.
FIG. 1 is a view which schematically shows a structure and an
equivalent circuit of a liquid crystal display device according to
an embodiment.
Specifically, the liquid crystal display device includes an
active-matrix-type liquid crystal display panel LPN. The liquid
crystal display panel LPN includes an array substrate AR which is a
first substrate, a counter-substrate CT which is a second substrate
that is disposed to be opposed to the array substrate AR, and a
liquid crystal layer LQ which is held between the array substrate
AR and the counter-substrate CT.
The liquid crystal display panel LPN includes an active area ACT
which displays an image. The active area ACT is composed of a
plurality of pixels PX which are arrayed in a matrix of m.times.n
(m and n are positive integers). In the present embodiment, the
active area ACT includes a transmissive display area A1 and a
reflective display area A2. The transmissive display area A1 and
reflective display area A2 are arranged, for example, along a
second direction Y. The transmissive display area A1 is an area
which displays an image, mainly by selectively passing backlight
which is incident on the liquid crystal display panel LPN. The
reflective display area A2 is an area which displays an image,
mainly by selectively reflecting ambient light which is incident on
the liquid crystal display panel LPN.
The liquid crystal display panel LPN includes, in the active area
ACT, an n-number of gate lines G (G1 to Gn), an n-number of storage
capacitance lines C (C1 to Cn), and an m-number of source lines S
(S1 to Sm). The gate lines G and storage capacitance lines C
extend, for example, substantially linearly in a first direction X.
The gate lines G and storage capacitance lines C are alternately
arranged along the second direction Y crossing the first direction
X. In this example, the first direction X and the second direction
Y are perpendicular to each other. The source lines S cross the
gate lines G and storage capacitance lines C. The source lines S
extend substantially linearly in the second direction Y. It is not
always necessary that each of the gate lines G, storage capacitance
lines C and source lines S extend linearly, and a part thereof may
be bent.
Each of the gate lines G is led out of the active area ACT and is
connected to a gate driver GD. Each of the source lines S is led
out of the active area ACT and is connected to a source driver SD.
At least parts of the gate driver GD and source driver SD are
formed on, for example, the array substrate AR, and the gate driver
GD and source driver SD are connected to a driving IC chip 2 which
incorporates a controller.
Each of the pixels PX includes a switching element SW, a pixel
electrode PE and a common electrode CE. A storage capacitance CS is
formed, for example, between the storage capacitance line C and the
pixel electrode PE. The storage capacitance line C is electrically
connected to a voltage application module VCS to which a storage
capacitance voltage is applied.
In the present embodiment, the liquid crystal display panel LPN is
configured such that the pixel electrodes PE are formed on the
array substrate AR, and at least a part of the common electrode CE
is formed on the counter-substrate CT, and liquid crystal molecules
of the liquid crystal layer LQ are switched by mainly using an
electric field which is produced between the pixel electrodes PE
and the common electrode CE.
The switching element SW is composed of, for example, an n-channel
thin-film transistor (TFT). The switching element SW is
electrically connected to the gate line G and source line S. The
switching element SW may be of a top gate type or a bottom gate
type. In addition, a semiconductor layer of the switching element
SW is formed of, for example, polysilicon, but it may be formed of
amorphous silicon.
The pixel electrodes PE are disposed in the respective pixels PX,
and are electrically connected to the switching elements SW. The
common electrode CE is disposed common to the pixel electrodes PE
of plural pixels PX via the liquid crystal layer LQ. The array
substrate AR includes a power supply module VS for applying a
voltage to the common electrode CE. The power supply module VS is
formed, for example, on the outside of the active area ACT. The
common electrode CE is led out to the outside of the active area
ACT, and is electrically connected to the power supply module VS
via an electrically conductive member (not shown).
FIG. 2 is a cross-sectional view, taken along line II-II in FIG. 1,
which schematically illustrates an example of a cross section of
the liquid crystal display panel LPN shown in FIG. 1. FIG. 2 shows
only parts which are necessary for the description.
In the transmissive display area A1, a backlight 4 is disposed on
the back side of the array substrate AR which constitutes the
liquid crystal display panel LPN. Various modes are applicable to
the backlight 4. As the backlight 4, use may be made of either a
backlight which utilizes a light-emitting diode (LED) as a light
source, or a backlight which utilizes a cold cathode fluorescent
lamp (CCFL) as a light source. A description of the detailed
structure of the backlight 4 is omitted.
The array substrate AR is formed by using a first insulative
substrate 10 having light transmissivity. Gate lines G and storage
capacitance lines C are formed on the first insulative substrate
10, and are covered with a first interlayer insulation film 11.
Source lines (not shown) are formed on the first interlayer
insulation film 11 and are covered with a second interlayer
insulation film 12. Pixel electrodes PE are formed on the second
interlayer insulation film 12.
The pixel electrodes PE include transmissive pixel electrodes PET
disposed in the transmissive display area A1, and reflective pixel
electrodes PER disposed in the reflective display area A2. The
transmissive pixel electrodes PET are formed of a transparent,
electrically conductive material such as indium tin oxide (ITO) or
indium zinc oxide (IZO), so as to pass light from the backlight 4.
The reflective pixel electrodes PER reflect ambient light, which
has entered the liquid crystal display panel LPN from the
counter-substrate CT side, back to the counter-substrate CT side.
Specifically, the reflective pixel electrodes PER are formed of an
opaque, electrically conductive material such as aluminum (A1),
which reflects light. Incidentally, the surface of the reflective
pixel electrode PER is formed to have such asperities as to avoid
mirror reflection.
A first alignment film AL1 is disposed on that surface of the array
substrate AR, which is opposed to the counter-substrate CT, and the
first alignment film AL1 extends over substantially the entirety of
the active area ACT. The first alignment film AL1 covers the pixel
electrode PE, etc., and is also disposed on the second interlayer
insulation film 12.
The counter-substrate CT is formed by using a second insulative
substrate 20 having light transmissivity. The counter-substrate CT
includes a black matrix BM, a color filter CF, an overcoat layer
OC, a projection 22, a common electrode CE and a second alignment
film AL2.
The black matrix BM partitions each pixel PX and forms an aperture
portion AP which is opposed to the pixel electrode PE.
Specifically, the black matrix BM is disposed so as to be opposed
to wiring portions, such as the source lines, gate lines G, storage
capacitance lines C and switching elements. In the example
illustrated, only the portions of the black matrix BM, which extend
in the first direction X, are shown, but the black matrix BM may
also include portions extending in the second direction Y. The
black matrix BM is disposed on an inner surface 20A of the second
insulative substrate 20, which is opposed to the array substrate
AR.
The color filter CF is disposed in association with each pixel PX.
Specifically, the color filter CF is disposed in the aperture
portion AP on the inner surface 20A of the second insulative
substrate 20, and a part of the color filter CF extends over the
black matrix BM. Color filters CF, which are disposed in the pixels
PX neighboring in the first direction X, have mutually different
colors. For example, the color filters CF are formed of resin
materials which are colored in three primary colors of red, blue
and green. A red color filter CF(R), which is formed of a resin
material that is colored in red, is disposed in association with a
red pixel. A blue color filter CF(B), which is formed of a resin
material that is colored in blue, is disposed in association with a
blue pixel. A green color filter CF(G), which is formed of a resin
material that is colored in green, is disposed in association with
a green pixel. Boundaries between these color filters CF are
located at positions overlapping the black matrix BM.
The overcoat layer OC covers the color filters CF. The overcoat
layer OC reduces the effect of asperities on the surface of the
color filters CF.
The projection 22 is disposed, in the reflective display area A2,
on that side of the overcoat layer OC, which is opposed to the
array substrate AR. The projection 22 is formed of, for example, a
transparent resin material. The thickness of the projection 22 is
set in accordance with the thickness of the liquid crystal layer LQ
in the reflective display area A2. The retardation of the liquid
crystal layer LQ in the reflective display area A2 is made to
substantially equal to the retardation of the liquid crystal layer
LQ in the transmissive display area A1, by adjusting the thickness
of the projection 22. Specifically, the thickness of the projection
22 is set so that the thickness of the liquid crystal layer LQ in
the reflective display area A2 may become smaller than the
thickness of the liquid crystal layer LQ in the transmissive
display area A1. Preferably, the thickness of the projection 22 is
set so that the thickness of the liquid crystal layer LQ in the
reflective display area A2 may become about 1/2 of the thickness of
the liquid crystal layer LQ in the transmissive display area
A1.
The common electrode CE is formed of a transparent, electrically
conductive material such as ITO or IZO. The common electrode CE is
formed over the transmissive display area A1 and reflective display
area A2. To be more specific, the common electrode CE is formed on
that side of the overcoat layer OC in the transmissive display area
A1, which is opposed to the array substrate AR, and is formed on
that side of the projection 22 in the reflective display area A2,
which is opposed to the array substrate AR. A third direction Z is
a direction perpendicular to the first direction X and second
direction Y, or is a normal direction of the liquid crystal display
panel LPN.
A second alignment film AL2 is disposed on that surface of the
counter-substrate CT, which is opposed to the array substrate AR,
and the second alignment film AL2 extends over substantially the
entirety of the active area ACT. The second alignment film AL2
covers the common electrode CE, overcoat layer OC and projection
22.
The first alignment film AL1 and second alignment film AL2 are
subjected to, where necessary, alignment treatment (e.g. rubbing
treatment or optical alignment treatment) for initially aligning
the liquid crystal molecules of the liquid crystal layer LQ. In the
transmissive display area A1, a first alignment treatment direction
PD1 (shown in FIG. 3), in which the first alignment film AL1
initially aligns the liquid crystal molecules, and a second
alignment treatment direction PD2 (shown in FIG. 3), in which the
second alignment film AL2 initially aligns the liquid crystal
molecules, are parallel to each other and are opposite or identical
to each other. In the example illustrated, the first alignment
treatment direction PD1 and the second alignment treatment
direction PD2 are, for example, parallel to the second direction Y
and opposite to each other. By performing such alignment treatment,
multiple domains are formed in one pixel, and a viewing angle
characteristic is improved.
In the meantime, in the reflective display area A2, when the liquid
crystal alignment mode is set to be, for example, a vertical
alignment (VA) mode, vertical alignment films, which are
pre-treated so as to align liquid crystal molecules in a vertical
direction, are used for the first alignment film AL1 and second
alignment film AL2 in the reflective display area A2. Thus, there
is no need to perform alignment treatment.
The above-described array substrate AR and counter-substrate CT are
disposed such that their first alignment film AL1 and second
alignment film AL2 are opposed to each other. Specifically, the
projection 22 of the counter-substrate CT is disposed to be opposed
to plural reflective pixel electrodes PER. In this case, columnar
spacers, which are formed of, e.g. a resin material so as to be
integral to one of the array substrate AR and counter-substrate CT,
are disposed between the first alignment film AL1 of the array
substrate AR and the second alignment film AL2 of the
counter-substrate CT. Thereby, a predetermined cell gap is created.
The cell gap in the transmissive display area A1 is, for example, 2
to 7 .mu.m, and the cell gap in the reflective display area A2 is
about 1/2 of the cell gap in the transmissive display area A1. The
array substrate AR and counter-substrate CT are attached by a
sealant SB on the outside of the active area ACT in the state in
which the predetermined cell gap is created therebetween.
The liquid crystal layer LQ is held in the cell gap which is
created between the array substrate AR and the counter-substrate
CT, and is disposed between the first alignment film AL1 and second
alignment film AL2. The liquid crystal layer LQ is composed of, for
example, a liquid crystal material having a positive
(positive-type) dielectric constant anisotropy.
A first optical element OD1 including a first polarizer PL1 is
attached to an outer surface of the array substrate AR, for
example, an outer surface 10B of the first insulative substrate 10,
by an adhesive or the like. The first optical element OD1 is a
linear polarizer which is located on that side of the liquid
crystal display panel LPN, which is opposed to the backlight 4, and
controls the polarization state of incident light which enters the
liquid crystal display panel LPN from the backlight 4. The first
polarizer PL1 is a linear polarizer having a first polarization
axis (or first absorption axis) AX1.
A second optical element OD2 is attached to an outer surface of the
counter-substrate CT, for example, an outer surface 20B of the
second insulative substrate 20 by an adhesive or the like. The
second optical element OD2 is located on the display surface side
of the liquid crystal display panel LPN, and controls the
polarization state of emission light emerging from the liquid
crystal display panel LPN and the polarization state of ambient
light entering the liquid crystal display panel LPN. The second
optical element OD2 includes a second polarizer PL2 which is
disposed over the transmissive display area A1 and reflective
display area A2, and a retardation plate 25 which is disposed in
the reflective display area A2. The retardation plate 25 imparts a
phase difference of 1/2 wavelength to the transmissive light. The
retardation plate 25 is disposed between the outer surface 20B of
the second insulative substrate 20 and the second polarizer
PL2.
In the meantime, in the transmissive display area A1, a plate
member, which is formed of a transparent resin material or the
like, may be disposed between the outer surface 20B of the second
insulative substrate 20 and the second polarizer PL2. The plate
member 26 has substantially no phase difference, and has no
function as a retardation plate. The thickness of the plate member
26 is equal to the thickness of the retardation plate 25. By
disposing the plate member 26, no gap occurs between the second
polarizer PL2 and the second insulative substrate 20 in the
transmissive display area A1, and no stepped portion occurs at a
boundary between the transmissive display area A1 and reflective
display area A2.
In FIG. 2, the second polarizer PL2 is disposed as one body over
the transmissive display area A1 and reflective display area A2.
Alternatively, the second polarizer PL2 may is disposed as separate
bodies disposed in the transmissive display area A1 and reflective
display area A2, respectively. The second polarizer PL2 is a linear
polarizer having a second polarization axis (or second absorption
axis) AX2.
The first polarization axis AX1 and the second polarization axis
AX2 have a substantially orthogonal positional relationship
(crossed Nicols). In this case, one of the polarizers is disposed,
for example, such that the polarization axis thereof is parallel or
perpendicular to the initial alignment direction of liquid crystal
molecules in the transmissive display area A1, that is, to the
first alignment treatment direction PD1 or second alignment
treatment direction PD2. When the initial alignment direction is
parallel to the second direction Y, the polarization axis of one of
the polarizers is parallel to the second direction Y or is parallel
to the first direction X.
In an example shown in part (a) of FIG. 3, the first polarizer PL1
is disposed such that the first polarization axis AX1 thereof is
perpendicular to the second direction Y. The second polarizer PL2
is disposed such that the second polarization axis AX2 thereof is
parallel to the second direction Y. In an example shown in part (b)
of FIG. 3, the second polarizer PL2 is disposed such that the
second polarization axis AX2 thereof is perpendicular to the second
direction Y. The first polarizer PL1 is disposed such that the
first polarization axis AX1 thereof is parallel to the second
direction Y.
Furthermore, a protection plate 3 may be disposed on the outer
surface side of the second polarizer PL2. The protection plate 3
has, for example, a planar plate shape, and is disposed to be
opposed to the second polarizer PL2. The protection plate 3
includes light-shield portions 31. The light-shield portions 31 are
disposed, respectively, on an outside of the active area ACT, and
at a boundary between the transmissive display area A1 and
reflective display area A2. The light-shield portion 31 blocks leak
light due to a disturbance in alignment state of the liquid crystal
at the boundary part between the transmissive display area A1 and
reflective display area A2. Thus, degradation in display quality
can be avoided.
Incidentally, the protection plate 3 may function as a sensor
substrate. For example, the protection plate 3 may include a touch
sensor TS, such as a resistance-type touch sensor which detects an
electrical touch position, an electrostatic-capacitance-type touch
sensor which detects a capacitance change position, or an optical
touch sensor which is configured such that optical sensors are
formed in a matrix in the display device and detects a light amount
change position. Besides, a part of the sensor substrate may be
incorporated in the liquid crystal display panel LPN.
FIG. 3 is a plan view which schematically illustrates a structure
example of one pixel PX at a time when the transmissive display
area A1 of the liquid crystal display panel LPN shown in FIG. 1 is
viewed from the counter-substrate side. FIG. 3 is a plan view in an
X-Y plane.
The pixel PX illustrated has a rectangular shape having a less
length in the first direction X than in second direction Y, as
indicated by a broken line. A gate line G1 and a gate line G2
extend in the first direction X. A storage capacitance line C1 is
disposed between the gate line G1 and the gate line G2 and extends
in the first direction X. A source line S1 and a source line S2
extend in the second direction Y. A transmissive pixel electrode
PET is disposed between the neighboring source line S1 and source
line S2. In addition, the transmissive pixel electrode PET is
disposed between the gate line G1 and gate line G2.
In the example illustrated, in the pixel PX, the gate line G1 is
disposed at an upper side end portion, the gate line G2 is disposed
at a lower side end portion, the source line S1 is disposed at a
left side end portion, and the source line S2 is disposed at a
right side end portion. Strictly speaking, the gate line G1 is
disposed to extend over a boundary between the pixel PX and a pixel
neighboring on the upper side, the gate line G2 is disposed to
extend over a boundary between the pixel PX and a pixel neighboring
on the lower side, the source line S1 is disposed to extend over a
boundary between the pixel PX and a pixel neighboring on the left
side, and the source line S2 is disposed to extend over a boundary
between the pixel PX and a pixel neighboring on the right side. The
storage capacitance line C1 is disposed at a substantially central
part of the pixel.
The switching element SW in the illustrated example is electrically
connected to the gate line G1 and source line S1. The switching
element SW is provided at an intersection between the gate line G1
and source line S1. A drain line of the switching element SW is
formed to extend along the source line S1 and storage capacitance
line C1, and is electrically connected to the pixel electrode PE
via a contact hole CH which is formed at an area overlapping the
storage capacitance line C1. The switching element SW is provided
in an area overlapping the source line S1 and storage capacitance
line C1, and does not substantially protrude from the area
overlapping the source line S1 and storage capacitance line C1,
thus suppressing a decrease in area of an aperture portion which
contributes to display.
The transmissive pixel electrode PET includes a main pixel
electrode PA and a contact portion PC which are electrically
connected to each other. The main pixel electrode PA is formed in a
strip shape, and linearly extends in the second direction Y from
the contact portion PC to the vicinity of the upper side end
portion of the pixel PX and to the vicinity of the lower side end
portion of the pixel PX. The main pixel electrode PA is formed in a
strip shape having a substantially uniform width in the first
direction X. The contact portion PC is located at an area
overlapping the storage capacitance line C1, and is electrically
connected to the switching element SW via the contact hole CH. The
contact portion PC is formed to have a greater width than the main
pixel electrode PA. In the example illustrated, the transmissive
pixel electrode PET is formed in a cross shape.
The transmissive pixel electrode PET is disposed at a substantially
middle position between the source line S1 and source line S2, that
is, at a center of the pixel PX. The distance in the first
direction X between the source line S1 and the main pixel electrode
PA is substantially equal to the distance in the first direction X
between the source line S2 and the main pixel electrode PA.
The common electrode CE includes main common electrodes CA in the
transmissive display area A1. The main common electrodes CA extend,
in the X-Y plane, linearly in the second direction Y that is
substantially parallel to the main pixel electrode PA, on both
sides of the main pixel electrode PA. Alternatively, the main
common electrodes CA are opposed to the source lines S, and extend
substantially in parallel to the main pixel electrode PA. The main
common electrode CA is formed in a strip shape having a
substantially uniform width in the first direction X.
In the example illustrated, two main common electrodes CA are
arranged in parallel along the first direction X, and are disposed
at both the left side end portion and the right side end portion of
the pixel PX. In the description below, in order to distinguish
these main common electrodes CA, the left main common electrode in
the Figure is referred to as "CAL", and the right main common
electrode in the Figure is referred to as "CAR". The main common
electrode CAL is opposed to the source line S1, and the main common
electrode CAR is opposed to the source line S2. The main common
electrode CAL and the main common electrode CAR are electrically
connected to each other within the active area or outside the
active area. In the pixel PX, the main common electrode CAL is
disposed at the left side end portion, and the main common
electrode CAR is disposed at the right side end portion. Strictly
speaking, the main common electrode CAL is disposed to extend over
a boundary between the pixel PX and a pixel neighboring on the left
side, and the main common electrode CAR is disposed to extend over
a boundary between the pixel PX and a pixel neighboring on the
right side.
Paying attention to the positional relationship between the pixel
electrode PE and the main common electrodes CA, the pixel electrode
PE and the main common electrodes CA are alternately arranged along
the first direction X. The main pixel electrode PA and the main
common electrodes CA are disposed substantially in parallel to each
other. In this case, in the X-Y plane, each of the main common
electrodes CA does not overlap the pixel electrode PE.
Specifically, one pixel electrode PE is located between the main
common electrode CAL and main common electrode CAR which neighbor
each other. In other words, the main common electrode CAL and main
common electrode CAR are disposed on both sides of a position
immediately above the pixel electrode PE. Alternatively, the pixel
electrode PE is disposed between the main common electrode CAL and
main common electrode CAR. Thus, the main common electrode CAL,
main pixel electrode PA and main common electrode CAR are arranged
in the named order along the first direction X. The distance in the
first direction X between the pixel electrode PE and common
electrode CE is substantially uniform. Specifically, the distance
between the main common electrode CAL and the main pixel electrode
PA in the first direction X is substantially equal to the distance
between the main common electrode CAR and the main pixel electrode
PA in the first direction X. In the X-Y plane, an aperture portion,
which can pass backlight, is formed between the main pixel
electrode PA and the main common electrode CA.
FIG. 4 is a plan view which schematically illustrates a structure
example of one pixel PX at a time when the reflective display area
A2 of the liquid crystal display panel LPN shown in FIG. 1 is
viewed from the counter-substrate side. FIG. 4 is a plan view in
the X-Y plane. In the description below, a description of the same
structure as in the pixel PX in the above-described transmissive
display area A1 is omitted.
Like the transmissive display area A1, the pixel PX illustrated has
a rectangular shape having a less length in the first direction X
than in second direction Y, as indicated by a broken line. A gate
line Gi and a gate line Gi+1 extend in the first direction X. A
storage capacitance line Ci is disposed between the gate line Gi
and the gate line Gi+1 and extends in the first direction X. A
source line S1 and a source line S2 extend in the second direction
Y.
The switching element SW in the illustrated example is electrically
connected to the gate line Gi and source line S1. The switching
element SW is provided at an intersection between the gate line Gi
and source line S1. A drain line of the switching element SW is
formed to extend along the source line S1 and storage capacitance
line Ci, and is electrically connected to the reflective pixel
electrode PER via a contact hole CH which is formed at an area
overlapping the storage capacitance line Ci.
The reflective pixel electrode PER is an electrode with a planar
plate shape, and has a substantially rectangular shape having a
less length in the first direction X than in second direction Y.
Specifically, the reflective pixel electrode PER extends over
substantially the entirety of the pixel PX, and is disposed between
the neighboring source line S1 and source line S2 and between the
neighboring gate line Gi and gate line Gi+1. In other words,
substantially no gap is created between the reflective pixel
electrode PER and the source line or between the reflective pixel
electrode PER and the gate line. In the example illustrated, end
portions along the second direction Y of the reflective pixel
electrode PER overlap the source line S1 and source line S2, and
end portions along the first direction X of the reflective pixel
electrode PER overlap the gate line Gi and gate line Gi+1.
The common electrode CE includes a plate common electrode CB with a
planar plate shape in the reflective display area A2. Specifically,
the planar plate-shaped common electrode CB is opposed to the
reflective pixel electrode PER. In addition, the planar
plate-shaped common electrode CB is opposed to the source line S1,
source line S2, gate line Gi and gate line Gi+1. To be more
specific, the planar plate-shaped common electrode CB is disposed
to extend over substantially the entirety of the reflective display
area A2, so as to face not only the illustrated reflective pixel
electrode PER but also plural reflective pixel electrodes PER.
FIG. 5 is a cross-sectional view of the liquid crystal display
panel LPN at a time when the transmissive display area A1 is cut
along line A-A in FIG. 3, and a cross-sectional view of the liquid
crystal display panel LPN at a time when the reflective display
area A2 is cut along line B-B in FIG. 4.
In the array substrate AR, each source line S is formed on the
first interlayer insulation film 11 and is covered with the second
interlayer insulation film 12. The transmissive pixel electrode PET
and reflective pixel electrode PER are formed on the second
interlayer insulation film 12 and are covered with the first
alignment film AL1.
In the counter-substrate CT, the black matrix BM is located
immediately above the source line S. The main common electrode CA
of the common electrode CE is located immediately above the source
line S or immediately below the black matrix BM, on the array
substrate AR side of the overcoat layer OC. The planar plate-shaped
common electrode CB of the common electrode CE is disposed in the
entire reflective display area A2, on the array substrate AR side
of the projection 22. The planar plate-shaped common electrode CB
is opposed to each reflective pixel electrode PER. The main common
electrode CA and planar plate-shaped common electrode CB are
electrically connected and have the same potential.
Next, the operation of the liquid crystal display panel LPN having
the above-described structure is described.
The alignment state of liquid crystal molecules LM at a time when
no voltage is applied, that is, in a state (OFF time) in which no
electric field is produced between the pixel electrode PE and
common electrode CE, is equal between the transmissive display area
A1 and the reflective display area A2. For example, when the first
alignment treatment direction PD1 is parallel and opposite to the
second alignment treatment direction PD2, the liquid crystal
molecules LM are homogeneously aligned. When the first alignment
treatment direction PD1 is parallel and identical to the second
alignment treatment direction PD2, the liquid crystal molecules LM
are splay-aligned.
At this time, in the transmissive display area A1, part of light
from the backlight 4 passes through the first polarizer PL1, and
enters the liquid crystal display panel LPN. The liquid crystal
layer LQ imparts no phase difference to the light passing at the
OFF time. Thus, the polarization state of the light, which has
passed through the liquid crystal display panel LPN, does not
change. Accordingly, at the OFF time, the light, which has passed
through the liquid crystal display panel LPN, is absorbed by the
second polarizer PL2 (black display).
In the reflective display area A2, part of light, which has passed
through the protection plate 3, passes through the second polarizer
PL2, passes through the retardation plate 25 and liquid crystal
display panel LPN, and is then reflected by the reflective pixel
electrode PER. The reflected light passes once again through the
retardation plate 25 and liquid crystal display panel LPN, and
enters the second polarizer PL2. The liquid crystal layer LQ of the
reflective display area A2 is configured to impart a phase
difference of 1/4 wavelength to the light passing at the OFF time.
Specifically, linearly polarized light, which has passed through
the second polarizer PL2, passes through the retardation plate 25
and liquid crystal layer LQ two times, and is given a phase
difference of 1/2 wavelength. The light with the phase difference
becomes linearly polarized light in a direction perpendicular to
the polarization direction of the second polarizer PL2, and enters
the second polarizer PL2. Thus, the light, which has passed through
the retardation plate 25 and liquid crystal layer LQ at the OFF
time, is absorbed by the second polarizer PL2 (black display).
On the other hand, in a state in which a voltage is applied to the
liquid crystal layer LQ, that is, in a state (ON time) in which a
potential difference (or an electric field) is produced between the
pixel electrode PE and the common electrode CE, a lateral electric
field (or an oblique electric field), which is substantially
parallel to the substrates, is produced between the transmissive
pixel electrode PET and the common electrode CE in the transmissive
display area A1. Thus, the liquid crystal molecules LM of the
transmissive display area A1 are aligned in a direction different
from the direction in the initial alignment state. Part of light,
which has entered the liquid crystal display panel LPN from the
backlight 4, passes through the first polarizer PL1, and enters the
liquid crystal display panel LPN. The polarization state of the
light, which has entered the liquid crystal display panel LPN,
varies depending on the alignment state of the liquid crystal
molecules LM. At this ON time, at least part of the light emerging
from the liquid crystal layer LQ passes through the second
polarizer PL2 (white display).
In the reflective display area A2, a vertical electric field along
a normal direction of the substrates is produced between the
reflective pixel electrode PER and the common electrode CE. Thus,
the liquid crystal molecules LM of the reflective display area A2
are aligned in the normal direction of the substrates. Part of
light, which has passed through the protection plate 3, passes
through the second polarizer PL2, passes through the retardation
plate 25 and liquid crystal display panel LPN, and is then
reflected by the reflective pixel electrode PER. The reflected
light passes once again through the retardation plate 25 and liquid
crystal display panel LPN, and enters the second polarizer PL2. The
liquid crystal layer LQ is configured to impart no phase difference
to the light passing at the ON time. Specifically, linearly
polarized light, which has passed through the second polarizer PL2,
passes through the retardation plate 25 and liquid crystal layer LQ
two times and is given a phase difference of 1 wavelength, and the
linearly polarized light, which is parallel to the polarization
axis of the second polarizer PL2, enters the second polarizer PL2.
Thus, at the ON time, the light, which has passed through the
retardation plate 25 and liquid crystal layer LQ, passes through
the second polarizer PL2 (white display).
According to the present embodiment, there is no need to dispose a
backlight on the back side of the liquid crystal display panel LPN
in the reflective display area A2, and a liquid crystal display
device with reduced power consumption can be provided.
In the above embodiment, the liquid crystal mode in the
transmissive display area A1 may be an IPS mode or an FFS mode.
However, in the embodiment, it is possible to simultaneously
perform the fabrication step of forming the common electrode CE on
the counter-substrate CT in the transmissive display area A1, and
the fabrication step of forming the common electrode CE on the
counter-substrate CT in the reflective display area A2. Thus, the
number of fabrication steps can be made smaller than in the IPS
mode or FFS mode. Besides, it is possible to adopt, in the
transmissive display area A1, a liquid crystal mode which controls
the alignment state of the liquid crystal by making use of a
vertical electric field.
In the above-described embodiment, any of liquid crystal modes,
which control the alignment state of the liquid crystal by making
use of the vertical electric field, can be adopted as the liquid
crystal mode in the reflective display mode A2. In the reflective
display area A2, it should suffice if the liquid crystal layer LQ
is configured such that the phase difference of the passing light
at the ON time is zero and the phase difference of the passing
light at the OFF time is 1/4 wavelength.
In particular, if an electrically controlled birefringence (ECB)
mode, which makes use of horizontal alignment (homogeneous
alignment) or the like, is used in the reflective display area A2,
matching with the liquid crystal mode of the electrode structure in
the transmissive display area A1 shown in FIG. 3 can advantageously
be obtained.
According to the present embodiment, a high transmittance can be
obtained in the inter-electrode gap between the transmissive pixel
electrode PET and the common electrode CE in the transmissive
display area A1. In addition, a transmittance per pixel can
sufficiently be increased by increasing the inter-electrode
distance between the main pixel electrode PA and the main common
electrode CA. As regards product specifications in which the pixel
pitch is different, the peak condition of the transmittance
distribution can be used by varying the inter-electrode distance
(e.g. by varying the position of disposition of the main common
electrode CA in relation to the main pixel electrode PA).
Specifically, in the display mode in the transmissive display area
A1 of the present embodiment, products with various pixel pitches
can be provided by setting the inter-electrode distance, without
necessarily requiring fine electrode processing, as regards the
product specifications from low-resolution product specifications
with a relatively large pixel pitch to high-resolution product
specifications with a relatively small pixel pitch. Therefore,
requirements for high transmittance and high resolution can easily
be realized.
According to the present embodiment, in the transmissive display
area A1, the transmittance is sufficiently lowered in the region
overlapping the black matrix BM. Thus, even when the colors of the
color filters are different between neighboring pixels, the
occurrence of color mixture can be suppressed, and the decrease in
color reproducibility or the decrease in contrast ratio can be
suppressed.
When misalignment occurs between the array substrate AR and the
counter-substrate CT, there are cases in which, in the transmissive
display area A1, a difference occurs in the distance between the
transmissive pixel electrode PET and the common electrodes CE on
both sides of the pixel electrode PE. However, since such
misalignment commonly occurs in all pixels PX, the electric field
distribution does not differ between the pixels PX, and the
influence on the display of images is very small.
According to the present embodiment, in the transmissive display
area A1, the main common electrodes CA are opposed to the source
lines S. In particular, when the main common electrodes CA are
disposed immediately above the source lines S, respectively, the
aperture portion AP can be increased and the transmittance of the
pixel PX can be improved, compared to the case in which the main
common electrodes CA are disposed on the transmissive pixel
electrode PET side of the source lines S. Furthermore, by disposing
the main common electrodes CA immediately above the source lines S,
respectively, the inter-electrode distance between the transmissive
pixel electrode PET, on one hand, and the main common electrodes
CA, on the other hand, can be increased, and a lateral electric
field, which is closer to a horizontal lateral electric field, can
be produced. Therefore, a wide viewing angle, which is the
advantage of an IPS mode, etc. in the conventional structure, can
be maintained.
The above-described example is directed to the case where the
initial alignment direction of liquid crystal molecules LM is
parallel to the second direction Y. However, the initial alignment
direction of liquid crystal molecules LM may be an oblique
direction D which obliquely crosses the second direction Y, as
shown in FIG. 3. An angle .theta.1 formed between the second
direction Y and the initial alignment direction D is greater than
0.degree. and is less than 45.degree.. From the standpoint of
alignment control of liquid crystal molecules LM, it is very
effective that the angle .theta.1 is about 5.degree. to 30.degree.,
preferably 20.degree. or less. Specifically, it is desirable that
the initial alignment direction of liquid crystal molecules LM be
substantially parallel to a direction in a range of 0.degree. or
more and 20.degree., relative to the second direction Y.
The above-described example relates to the case in which the liquid
crystal layer LQ is composed of a liquid crystal material having a
positive (positive-type) dielectric constant anisotropy.
Alternatively, the liquid crystal layer LQ may be composed of a
liquid crystal material having a negative (negative-type)
dielectric constant anisotropy. Although a detailed description is
omitted, in the case of the negative-type liquid crystal material,
since the positive/negative state of dielectric constant anisotropy
is reversed, it is desirable that the above-described formed angle
.theta.1 be in a range of between 45.degree. and 90.degree.,
preferably 70.degree. or more.
In the transmissive display area A1 of the embodiment, in the case
where the direction, in which the main pixel electrode PA and main
common electrode CA linearly extend, is parallel to the alignment
treatment direction of the first alignment film and second
alignment film, the liquid crystal molecules LM scarcely move from
the initial alignment direction even at the ON time, like the OFF
time, in the region overlapping the transmissive pixel electrode
PET or common electrode CE. Thus, even if the transmissive pixel
electrode PET and common electrode CE are formed of a
light-transmissive, electrically conductive material such as ITO,
little backlight passes through these regions, and these regions
hardly contribute to display at the ON time. Accordingly, the
transmissive pixel electrode PET and common electrode CE do not
necessarily need to be formed of a transparent, electrically
conductive material, and may be formed of an opaque, electrically
conductive material such as aluminum, silver or copper. Thus, as
regards the pixel electrode PE, the transmissive pixel electrode
PET may be formed of the same electrically conductive material as
the reflective pixel electrode PER, that is, an opaque,
electrically conductive material. In the case of the structure in
which both the transmissive pixel electrode PET and reflective
pixel electrode PER are formed on the second interlayer insulation
film 12 and are covered with the first alignment film AL1, the
transmissive pixel electrode PET and reflective pixel electrode PER
can be formed in the same fabrication step by using the same
electrically conductive material. Therefore, in the structure of
the embodiment, compared to the structure of other liquid crystal
modes, the number of fabrication steps can further be reduced.
Next, other embodiments will be described.
FIG. 6 is another cross-sectional view of the liquid crystal
display panel LPN at a time when the transmissive display area A1
is cut along line A-A in FIG. 3, and another cross-sectional view
of the liquid crystal display panel LPN at a time when the
reflective display area A2 is cut along line B-B in FIG. 4.
The example illustrated in FIG. 6 differs from the example
illustrated in FIG. 5 in that the array substrate AR includes
shield electrodes SL in the transmissive display area A1. The
structure of the reflective display area A2 is the same as the
structure shown in FIG. 5.
The shield electrodes SL are formed, for example, on the second
interlayer insulation film 12. Specifically, the shield electrodes
SL, together with the transmissive pixel electrode PET and
reflective pixel electrode PER, are covered with the first
alignment film AL1. The shield electrodes SL are opposed to the
source lines S and are located immediately below the main common
electrodes CA. Specifically, the shield electrodes SL extend in
parallel to the source lines S and main common electrodes CA. The
shield electrodes SL have the same potential as the common
electrodes CE. By providing the shield electrodes SL, an undesired
electric field from the source lines S can be shielded, and
degradation in display quality can further be suppressed. In
addition, the shield electrodes SL can be formed of the same
material in the same fabrication step as the transmissive pixel
electrodes PET, etc.
Incidentally, the array substrate AR may include, in the
transmissive display area A1, shield electrodes which are opposed
to the gate lines G. By providing such shield electrodes, an
undesired electric field from the gate lines G can be shielded, and
degradation in display quality can further be suppressed.
FIG. 7 is another cross-sectional view of the liquid crystal
display panel LPN at a time when the transmissive display area A1
is cut along line A-A in FIG. 3, and another cross-sectional view
of the liquid crystal display panel LPN at a time when the
reflective display area A2 is cut along line B-B in FIG. 4.
The example illustrated in FIG. 7 differs from the example
illustrated in FIG. 6 in that the counter-substrate CT does not
include the main common electrodes in the transmissive display area
A1. The structure of the reflective display area A2 is the same as
the structure shown in FIG. 5.
In the transmissive display area A1 of the counter-substrate CT,
that surface of the overcoat layer OC, which is located on the
array substrate AR side, is entirely covered with the second
alignment film AL2. In this example, at the ON time, a vertical
electric field, which controls the alignment of liquid crystal
molecules LM, is formed between the reflective pixel electrodes PER
and common electrode CE in the reflective display area A2, as
described above, while a lateral electric field, which controls the
alignment of liquid crystal molecules LM, is formed between the
transmissive pixel electrodes PET and shield electrodes in the
transmissive display area A1. In this example, like the
above-described embodiment, the alignment state of liquid crystal
molecules LM is controlled in the transmissive display area A1, and
the same advantageous effects as described above can be
obtained.
As has been described above, according to the present embodiment, a
liquid crystal display device, which reduces power consumption, can
be provided.
While certain embodiments have been described, these embodiments
have been presented by way of example only, and are not intended to
limit the scope of the inventions. Indeed, the novel embodiments
described herein may be embodied in a variety of other forms;
furthermore, various omissions, substitutions and changes in the
form of the embodiments described herein may be made without
departing from the spirit of the inventions. The accompanying
claims and their equivalents are intended to cover such forms or
modifications as would fall within the scope and spirit of the
inventions.
* * * * *